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/*
* Copyright (c) 2018, ARM Limited and Contributors. All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <assert.h>
#include <string.h>
#include <lib/mmio.h>
#include <rpi_hw.h>
/* Initial amount of values to discard */
#define RNG_WARMUP_COUNT U(0x40000)
static void rpi3_rng_initialize(void)
{
uint32_t int_mask, ctrl;
/* Return if it is already enabled */
ctrl = mmio_read_32(RPI3_RNG_BASE + RPI3_RNG_CTRL_OFFSET);
if ((ctrl & RPI3_RNG_CTRL_ENABLE) != 0U) {
return;
}
/* Mask interrupts */
int_mask = mmio_read_32(RPI3_RNG_BASE + RPI3_RNG_INT_MASK_OFFSET);
int_mask |= RPI3_RNG_INT_MASK_DISABLE;
mmio_write_32(RPI3_RNG_BASE + RPI3_RNG_INT_MASK_OFFSET, int_mask);
/* Discard several values when initializing to give it time to warmup */
mmio_write_32(RPI3_RNG_BASE + RPI3_RNG_STATUS_OFFSET, RNG_WARMUP_COUNT);
mmio_write_32(RPI3_RNG_BASE + RPI3_RNG_CTRL_OFFSET,
RPI3_RNG_CTRL_ENABLE);
}
static uint32_t rpi3_rng_get_word(void)
{
size_t nwords;
do {
/* Get number of available words to read */
nwords = (mmio_read_32(RPI3_RNG_BASE + RPI3_RNG_STATUS_OFFSET)
>> RPI3_RNG_STATUS_NUM_WORDS_SHIFT)
& RPI3_RNG_STATUS_NUM_WORDS_MASK;
} while (nwords == 0U);
return mmio_read_32(RPI3_RNG_BASE + RPI3_RNG_DATA_OFFSET);
}
void rpi3_rng_read(void *buf, size_t len)
{
uint32_t data;
size_t left = len;
uint32_t *dst = buf;
assert(buf != NULL);
assert(len != 0U);
assert(check_uptr_overflow((uintptr_t) buf, (uintptr_t) len) == 0);
rpi3_rng_initialize();
while (left >= sizeof(uint32_t)) {
data = rpi3_rng_get_word();
*dst++ = data;
left -= sizeof(uint32_t);
}
if (left > 0U) {
data = rpi3_rng_get_word();
memcpy(dst, &data, left);
}
}
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